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Old 12-01-2012, 12:00 PM   #1
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Grounding With Metal Boxes


How do you guys do your ground? I've seen this a few times with metal boxes. They say you can ground on the wire nuts like that and then when the metal outlet tabs and screws are screwed into the metal box that it grounds itself without using the ground screw on the outlet and in the box. What are the pros/cons of this?


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Old 12-01-2012, 12:04 PM   #2
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Grounding With Metal Boxes


In side the box is a grounding screw, that is where it should be grounded both to the box and the device. The way it is now if by some chance the ground becomes hot it could melt the casing and start a toxic fire in the wall.

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Old 12-01-2012, 12:04 PM   #3
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Grounding With Metal Boxes


Doesn't seem like the most secure connection for a ground. Should make a pigtail from the box, pigtail to outlet ground screw, and connect those to incoming ground(s)
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Old 12-01-2012, 12:11 PM   #4
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In side the box is a grounding screw, that is where it should be grounded both to the box and the device. The way it is now if by some chance the ground becomes hot it could melt the casing and start a toxic fire in the wall.
Wouldn't it melt and cause a fire either way if the ground became hot?
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Old 12-01-2012, 12:12 PM   #5
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Grounding With Metal Boxes


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Wouldn't it melt and cause a fire either way if the ground became hot?
it won't melt.... the job of the grounding conductor is to clear a fault, in order to do this, it MUST become energized...

Why people throw out comments at will is beyond me.
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Old 12-01-2012, 12:15 PM   #6
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it won't melt.... the job of the grounding conductor is to clear a fault, in order to do this, it MUST become energized...

Why people throw out comments at will is beyond me.
So how wrong/dangerous is the picture?

It seems to be ok as long as you don't remove the outlets because then the ground would be gone?
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Old 12-01-2012, 12:15 PM   #7
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Grounding With Metal Boxes


The grounding install is all wrong, for whatever reason, that technique was used early on, but the grounding conductor must be made up inside the box, the metal box and device all bonded together.
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Old 12-01-2012, 12:16 PM   #8
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So how wrong/dangerous is the picture?

It seems to be ok as long as you don't remove the outlets because then the ground would be gone?
its far from okay, fix the issue.
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Old 12-01-2012, 12:17 PM   #9
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The grounding install is all wrong, for whatever reason, that technique was used early on, but the grounding conductor must be made up inside the box, the metal box and device all bonded together.
How long ago was that technique used?
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Old 12-01-2012, 12:18 PM   #10
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How long ago was that technique used?
A long time ago back when NM had a cloth jacket and it was done much nicer than in your picture, thats a new install, but some hack did the work.
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Old 12-01-2012, 12:20 PM   #11
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Grounding With Metal Boxes


Probably 40 years ago or more.

The sheath must extend into the box at least 1/4". All grounds need to be connected together and to the box and device.
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Old 12-01-2012, 01:13 PM   #12
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So how wrong/dangerous is the picture?

It seems to be ok as long as you don't remove the outlets because then the ground would be gone?
It is an incredibly sloppy application, there is no way that it is OK.
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Old 12-01-2012, 02:21 PM   #13
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Yes it is sloppy, but let's back up for a second. My entire house was grounded in a similar manner. House was built in 1959, I a guessing that the technique of wrapping wire around a screw on the outside of a metal box was pretty typical in 1959. And the technique likely violates current NEC requirements, since the grounding wire is apparently supposed to be connected to a green grounding screw inside the box. But the technique certainly works electrically, since the copper grounding wire is mechanically connected to the box.

Assuming the outlet grounding wire is connected to a grounding screw inside the box via a pigtail, the system is electrically grounded. I would class this as a technical violation of NEC, and if the wire was installed some years ago, it may have been compliant with regulations at the time, in which case it may be grandfathered. Is it worth fixing? Probably, but does not look like a really high priority. If the outlet is ungrounded, that is a more serious problem, but you can't tell from the photo.
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Old 12-01-2012, 02:25 PM   #14
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Yes it is sloppy, but let's back up for a second. My entire house was grounded in a similar manner. House was built in 1959, I a guessing that the technique of wrapping wire around a screw on the outside of a metal box was pretty typical in 1959. And the technique likely violates current NEC requirements, since the grounding wire is apparently supposed to be connected to a green grounding screw inside the box. But the technique certainly works electrically, since the copper grounding wire is mechanically connected to the box.

Assuming the outlet grounding wire is connected to a grounding screw inside the box via a pigtail, the system is electrically grounded. I would class this as a technical violation of NEC, and if the wire was installed some years ago, it may have been compliant with regulations at the time, in which case it may be grandfathered. Is it worth fixing? Probably, but does not look like a really high priority. If the outlet is ungrounded, that is a more serious problem, but you can't tell from the photo.
It's a hacked installation, and the yellow NM shows it's not an old installation. And ground screw does not have to be green.
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Old 12-01-2012, 02:32 PM   #15
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Grounding With Metal Boxes


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A long time ago back when NM had a cloth jacket and it was done much nicer than in your picture, thats a new install, but some hack did the work.
It was done back in the 50's through the 60's (when grounded cables became a requirement), primarily in the Northeast. And hence the name "Boston Back wrap". But even then the sheathe was brought into the box and the ground was wrapped tightly back around the cable and secured under the clamp. Even if done correctly it is no longer compliant.

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